cleanup: get rid of redundant assignments 'foo = foo'

Redundant assignments were searched with:

grep '^ *\(.*\) = \1$' `hg files`

Some of these cases have resulted from earlier cleanup, like:

foo = safe_unicode(foo)

and later batch removing safe_unicode usage. See e.g. commit
e35373106528b29461b7f5144780cb9ec79f765d .


Note: two false positives occur:

kallithea/tests/models/test_settings.py:39:
setting.app_settings_value = setting.app_settings_value
kallithea/tests/models/test_settings.py:42:
setting.app_settings_value = setting.app_settings_value

which is not a plain assignment but where 'app_settings_value' is a property
method with side effects.